1. Field of the Invention
The present invention relates to a die block assembly, and particularly to a die block assembly which prevents spring fragments from entering a clearance of the assembly.
2. The Related Art
In industrial stamping processes, a ram of a die block assembly often sticks to a stamped workpiece. To overcome this problem, auxiliary unloading structures have been developed for die block assemblies.
A conventional die block assembly is shown in FIG. 2. An upper die 100 of the die block assembly includes a fixing plate 102, an intermediate plate 104 and a clamping plate 106. The plates 102, 104, 106 are stacked and secured together using a plurality of upper bolts (not labeled). A plurality of receiving holes 108 (only one shown) is defined through the intermediate plate 104 and the clamping plate 106. Each hole 108 receives a spring 112. A plurality of rams 110 (only one shown) depends from a bottom surface of the clamping plate 106, for stamping a workpiece 150. An unloading plate 120 is connected to the clamping plate 106. A plurality of lower bolts 140 (only one shown) extends through corresponding bores (not labeled) of the clamping plate 106 to engage with the unloading plate 120, thereby connecting the clamping plate 106 to the unloading plate 120. The clamping plate 106 can move up and down around perimeters of the bolts 140. A plurality of through holes 122 (only one shown) is defined in the unloading plate 120, for receiving the corresponding rams 110 of the clamping plate 106.
In the stamping process, the upper die 100 moves downwardly so that the clamping plate 106 touches the unloading plate 120. The springs 112 are compressed, and the ram 110 completes stamping of the workpiece 150. When the upper die 100 moves back upwardly, the springs 112 return to their original position and abut against the unloading plate 120, thereby preventing the unloading plate 120 from moving upwardly. The rams 110 move upwardly relative to the unloading plate 120, and exit the workpiece 150. Thus the workpiece 150 is prevented from sticking to the rams 110.
The springs 112 used in the die block assembly tend to age and deform permanently over time. Eventually the springs fracture, producing very hard fragments 114 (only one shown). When the die block assembly vibrates, the fragments 114 are prone to enter a clearance between the clamping plate 106 and the unloading plate 120. Thus in subsequent stamping, the die block assembly is easily deformed or even fractured.
Therefore an improved die block assembly is needed to overcome the above-mentioned shortcomings of the prior art.
Accordingly, an object of the present invention is to provide a die block assembly which prevents damage being caused by spring fragments produced from springs thereof.
To achieve the above-mentioned object, a die block assembly of the present invention comprises an upper die, an unloading plate, a plurality of springs, and a plurality of spacer blocks. A plurality of receiving holes is defined in the upper die, for receiving the springs. A plurality of rams depends from the upper die, for stamping a workpiece. The unloading plate is movably connected under the upper die, and defines a plurality of through holes for accommodating the corresponding rams therein. Each spacer block is a stepped cylinder which comprises a base and a protrusion extending upwardly from the base. Each spring abuts against the base of the corresponding spacer block. A height of each base is slightly greater than a maximum clearance between the upper die and the unloading plate. The spacer block prevents spring fragments produced in the stamping process from entering the clearance.
Other objects, advantages and novel features of the present invention will be drawn from the. following detailed embodiment of the present invention with attached drawings, in which: